West Antarctic Glaciers Started Its Retreat in the 1940s

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A new study revealed that the present thinning and retreat of the floating Pine Island Glacier in West Antarctica could be a part of a longer-term process that may have been triggered in the 1940s.

The study, published in the journal Nature, showed that despite the weakening trend of different climate force, such as El Niño, the ice-sheet in the West Antarctic continues to retreat.

"This finding provided the first hint that the recent retreat could be part of a longer-term process that started decades or even centuries before satellite observations became available," explained James Smith of the British Antarctic Survey and lead author of the study, in a press release. "A period of warming in the Antarctic shelf waters triggered a substantial change in the ice sheet, via the mechanism that we see today -- that is, ocean-driven thinning and retreat of ice shelves leads to inland glacier acceleration and ice-sheet thinning."

For the study, the researchers access the cavity below the Pine Island Glacier by drilling 20-centimeter holes through the ice sheet. The researchers collected sediment cores at each drill site. These sediment cores can help the researchers determine and understand the transition of the Pine Island Glacier from being a grounded glacier into becoming a free floating ice.

The researchers then measured the amount of lead and plutonium in the sediment cores to determine when the ice retreat begun. The presence of plutonium in the sediment cores suggests that it has already begun its retreat during the onset of above-ground testing of nuclear weapons in 1950s.

Their findings suggests that the Pine Island Glacier has continuously experience thinning and retreat before the availability of observational records in 1992. This show that that the glaciers flowing in the Amundsen Sea sector have thinned in an accelerating rate over the past 40 years.

As one of the largest potential source of water, the thinning and retreat of the West Antarctic Ice Sheets could greatly contribute to the rising sea levels.